EP1062281B1 - Sulphide and oxysulphide pigments - Google Patents

Description

The present invention relates to sulfide and oxysulfide pigments on the Basis of platelet-shaped substrates with a sulfide or oxysulfide a rare earth metal and / or yttrium are coated, and their manufacture and use, especially in automotive paints, varnishes, Paints, plastics and cosmetic formulations.

Rare earth metal sulfide and yttrium sulfide pigments without a carrier and their use in plastics, paints and in cosmetics are known from EP 0 203 838 B1. In EP 0 545 746 B1 Described pigments that have a composition based on a Have sesquis sulfide of a rare earth metal or yttrium and contain a dopant at the same time.

In EP 0 620 254 B1, a pigment based on a rare earth metal sulfide is used or the yttrium sulfide as a support with a transparent Oxide, preferably a metal oxide, is coated.

These known rare earth metal sulfide or yttrium sulfide pigments are indeed usable as absorption pigments for many purposes but because of the lack of interference and lack of gloss not to be regarded as pearlescent pigments.

It was therefore an object of the present invention to provide rare earth metal sulfide or -oxysulfid- and yttriumsulfid- or -oxysulfidpigmente with good Provide opacity and strong colors, which is a broader Cover color spectrum and at the same time the properties related have the ability and interference of pearlescent pigments to interfere.

Surprisingly, it has now been found that coating of platelet-shaped substrates with sulfides or oxysulfides of the rare Earth metals (lanthanides) and yttrium pigments with interesting maintains coloristic and functional properties.

Uniform sulfide or Oxysulfide layers of rare earth metals and yttrium applied that have a high gloss and a pigment lend attractive powder color, and possibly the interference colors can produce thin platelets.

The invention thus relates, according to claim 1, to sulfide and oxysulfide pigments based on platelet-shaped substrates, characterized in that the substrates with a sulfide or oxysulfide of one or more rare earth metals and / or yttrium, of the formula M ₂ S ₃ or M ₂ S _3-x O _x , in which M denotes at least one element which is selected from the group formed by lanthanides and yttrium and is 2.5 <x <0.05, are coated.

The invention further relates to a method for producing the Pigments according to the invention according to claim 9 and the use of these pigments in Formulations such as paints, varnishes, printing inks, plastics and cosmetics.

The substrates are coated with a sulfide of rare earth metals or yttrium with the formula M ₂ S ₃ , wherein M is at least one element selected from the group consisting of the lanthanides of atomic numbers between 57 and 71 inclusive and yttrium. M ₂ S _{3 is} preferably a sesquis sulfide of the cubic γ-Ce ₂ S ₃ or γ-La ₂ S ₃ . However, sulfide mixtures, such as γ-Ce ₂ S ₃ and γ-La ₂ S ₃ , or mixed sulfides, such as LaYS ₃ , are also suitable. The coatings can also consist of oxysulfides of the formula M ₂ S _3-x O _x (2.5 <x <0.05).

All platelet-shaped materials known to the person skilled in the art which are stable under the coating conditions are suitable as the platelet-shaped base substrate. Natural and synthetic mica, kaolin, talc, vermiculite, TiO ₂ -, SiO ₂ -, Al ₂ O ₃ flakes, glass platelets, graphite, metal platelets, bismuth oxychloride, platelet-shaped iron oxide, LCPs (liquid crystal polymer pigments) are particularly worth mentioning here. holographic pigments and other platelet-like materials.

Mica, such as muscovite or phlogopite, is preferably used. However, materials which already have a metal oxide coating, in particular mica or SiO ₂ platelets with one or more coatings of, for example, TiO ₂ , ZrO ₂ , SnO ₂ , Al ₂ O ₃ , SiO ₂ , ZnO or, can also be used as the platelet-shaped substrate Mixtures of these metal oxides.

Thin metal platelets can also be used as substrate materials Question that partially - such as for Al platelets - with a layer of one low refractive index, stabilizing compound, such as silicon dioxide are. In addition to Al platelets, platelets can also be used as metal platelets made of Ag, Ti, Cu / Zn and other metals.

The size of these platelet-shaped substrates is not critical per se and particles can therefore be used in the one suitable for the intended application Size can be used. As a rule, the substrate is in Particle sizes of approximately 1 to 200 μm, in particular approximately 5 to 100 μm, deploy. The thickness of the particles is usually about 0.1 to 5 µm, in particular about 0.5 µm.

The starting materials used as substrates are known and can be produced by known processes. Mica particles of desired size can be determined by wet or dry Win mica and then classify it. Metal oxide Materials, especially metal oxide coated Mica flakes are both commercially available, e.g. from Merck KGaA, Darmstadt, as lriodin® pearlescent pigment or are known according to Process can be produced. Such methods are e.g. described in the Patents and patent applications US 3,087,828, US 3,087,829, DE 19 59 998, DE 20 09 566, DE 22 14 545, DE 22 44 298, DE 23 13 331, DE 25 22 572, DE 31 37 808, DE 31 37 809, DE 31 51 343, DE 31 51 354, DE 31 51 355, DE 32 11 602, DE 32 35 107, WO 93/08237 and EP 0 763 573.

The pigments according to the invention are prepared by adding a salt solution of a rare earth metal and / or yttrium and optionally oxalic acid to an aqueous suspension of a platelet-shaped substrate, the pH of the suspension optionally being kept largely constant in a range by the simultaneous addition of a base , which causes hydrolysis of the added salt, and which separates the pigment coated in this way with an oxide or oxide hydrate or oxalate, washes, dries, preferably 10 min. - 1.5 h at 80 - 150 ° C, and glows, preferably at 400 - 900 ° C. Finally, the product is in the H ₂ S gas stream or in the CS ₂ or H ₂ S / CS ₂ gas stream under inert gas at temperatures of 550 to 1200 ° C, preferably at 800 to 1000 ° C, 10 min. calcined to 2 h, wherein the oxalate or oxide of the rare earth metal and / or yttrium is converted into the sulfide or oxysulfide.

It is also possible to carry out the reaction with H ₂ S or CS ₂ in a fluidized bed reactor (CVD process).

As is generally the case for CVD processes, the use of a fluidized bed reactor or tube furnace is recommended for carrying out the CVD variant. The substrate particles to be coated are z. B. heated with fluidization (swirling) with an inert fluidizing gas such as N ₂ or argon to the desired reaction temperature (usually 400 to 900 ° C, preferably 650 to 850 ° C). The elemental sulfur or H ₂ S or CS ₂ is then introduced with the aid of inert carrier gas streams (advantageously partial streams of the fluidizing gas) from upstream evaporator vessels via separate nozzles, the sulfur concentration expediently being 0.5 to 5% by volume, preferably ≤ 2% by volume. %, based on the total amount of gas in the reactor.

In addition to sulfur-containing compounds, sulfur suppliers are preferred especially hydrogen sulfide and elemental sulfur to call.

When using elemental sulfur, you go procedural expediently so that finely ground sulfur powder, inertized for about 1 to 4 hours and then in the absence of oxygen to the reaction temperature, i. a. at 400-1200 ° C, preferably at 400-900 ° C, especially at 600-850 ° C, heated.

By depositing rare earth metal oxide or oxide hydrate layers or yttrium oxide or yttrium oxide hydrate layers in the presence of one or more dopants, for example selected from the group of alkaline earth and / or alkali metals, on the platelet-shaped substrates, particularly smooth, stable ones can be obtained , defined and colorful rare earth metal sulfide layers or yttrium sulfide layers are generated. The dopant is present in the form of an inclusion in the crystalline lattice of the sulfide layer M ₂ S ₃ or the oxysulfide layer M ₂ S _3-x O _x . The doping element can be selected alone or in mixtures from the salts of the alkali and / or alkaline earth metals, preferably sodium or potassium is used. When coating the platelet-shaped substrates with the oxide or oxide hydrate layer in solid form or in aqueous solution, the dopant is based on the substrate in amounts of 0.02 to 2.0% by weight, preferably 0.05 to 0.5% by weight .% added. The proportion of dopant in the sulfide layer or the oxysulfide layer is 0.01 to 1.0% by weight, preferably 0.05 to 0.5% by weight.

Platelet-shaped substrates which have a cerium sulfide layer are particularly preferred or have an oxysulfide layer and are doped with sodium.

The sulfide layer or oxysulfide layer of the rare earth metals or Depending on the desired effect, yttrium can have thicknesses of up to approximately 400 nm, preferably 10 to 300 nm. Thereby in the Rule levels of rare earth metal sulfides or yttrium sulfides or the corresponding oxysulfides achieved based on the substrate make up about 1 to 400% by weight, in particular 5 to 300% by weight. ever according to the layer thickness of the sulfide or oxysulfide layer Interference colors achieved with increasing layer thickness from silver over gold, red, violet and blue to green and finally interference colors go higher order.

For pigments that have a rare earth metal sulfide or yttrium sulfide layer or a corresponding oxysulfide layer further layers (preferably 3 to 7 layers) of high and low refractive index Materials (preferably oxides) and optionally semi-transparent Containing metals (multi-layer pigments) can be very strong angle-dependent Color effects (color flop, goniochromaticity) can be obtained.

It is also possible to coat the finished pigment or To undergo post-treatment, which is the light, weather and chemical Stability further increased, or handling of the pigment, in particular familiarization with different media is made easier. As re-coatings or post-treatments come, for example, in the DE-PS 22 15 191, DE-OS 31 51 354, DE-OS 32 35 017 or DE-OS 33 34 598 method described in question.

The additional substances applied make up only about 0.1 to 5% by weight, preferably about 0.5 to 3% by weight of the total pigment.

The pigments according to the invention are an important enrichment the technology. Due to the orange to red powder color and The interference color that can be generated arises extremely interesting Effects that can be used for a variety of applications being especially for substrates that already have an interference color have this through the sulfide layer or oxysulfide layer can be amplified and varied. Areas of application arise both in cosmetics, where the pigments according to the invention e.g. in Nail polishes, in make-up, gels, powders, ointments, emulsions, fat sticks and other agents in concentrations of generally 0.1 to 80% by weight can be used as well as in technology, e.g. for pigmentation of paints, varnishes, printing inks or plastics.

Plastics containing the pigments according to the invention in amounts of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, are outstandingly suitable for laser marking, for example with a CO ₂ or Nd-YAG laser. The markings obtained are characterized by their high contrast and sharp edges.

The following examples are intended to illustrate the invention without restricting it limit:

Examples example 1

100 g of mica with a particle size of 10 - 60 µm are suspended in 2 liters of water. A solution of 26 g of Ce (SO ₄ ) ₂ .4H ₂ O in 420 ml of dilute sulfuric acid is metered in at a pH of 5.5 and 60 ° C., the pH being constant by simultaneous dropwise addition of a 25% sodium hydroxide solution is held. The mixture is stirred for 0.5 h, the product is separated off, washed with water, dried at 80 ° C. for 0.5 h, calcined first at 500 ° C. in a stream of argon and finally at 950 ° C. in H _{2 for} 1 h S / argon flow (10 l / h H ₂ S).

The pigment obtained is characterized by its intense orange color and a high gloss.

Example 2

Analogously to Example 1, 100 g of SiO ₂ flakes with a particle size of 5 to 40 μm are coated with cerium sulfide. The pigment obtained is distinguished by an even more intense orange color and increased gloss compared to the pigment described in Example 1.

Example 3

Analogously to Example 1, 100 g of Iriodin® 103 rutile sterling silver (mica pigment coated with TiO ₂ with a particle size of 10 to 50 μm from Merck KGaA, Darmstadt) are coated with cerium sulfide. The pigment obtained has an intense orange-gold color and a high gloss.

Example 4

a) 100 g of mica with a particle size of 10-60 μm are suspended in 2 l of demineralized water and heated to 75 ° C. with constant stirring. The pH of the suspension is adjusted to 6.0 with dilute hydrochloric acid (20%). During the addition of 650 ml of an aqueous CeCl ₃ solution (108 g CeCl ₃ .7H ₂ O in 600 g demineralized water), the pH is kept constant at 6.0 with 20% sodium hydroxide solution. After the addition is complete stirred to complete the precipitation. The pigment obtained is filtered off, washed and dried at 110 ° C. The mica pigment coated with CeO ₂ is white in powder color and shows a slight silver interference.

b) 10 g of product from Example 4a) are placed in a quartz boat in a tube furnace with quartz tube. The furnace is heated to 650 ° C (200 cm ³ / min) under argon. Then H ₂ S gas is additionally passed through the system for ₁ hour. After the reaction has ended, the product is allowed to cool to room temperature with inertization (argon). A light red pigment with a γ-Ce ₂ S ₃ layer is obtained.

Example 5

10 g of product from Example 4a) are heated to 750 ° C. in a rotary tube oven under nitrogen (200 cm ³ / min) analogously to Example 4b). An H ₂ S stream (200 cm ³ / min) is then additionally passed through the system for 5 h. After the reaction has ended, the product is allowed to cool to room temperature with inertization (N ₂ ). The pigments thus obtained, coated with ceroxysulfide (Ce ₂ OS ₂ ), have a green body color and a high gloss.

Example 6

a) A mica suspension (100 g mica with a particle size of 10 - 60 µm) is separated, but at the same time a CeCl ₃ solution (68.4 g CeCl ₃ · 7 H ₂ O made up to 700 ml with deionized water) and an oxalic acid solution (H ₂ C ₂ O ₄ .2H ₂ O made up to 700 ml with deionized water) at 75 ° C. After the addition has ended, the pigments are washed, dried at 110 ° C. and annealed at 800 ° C.

b) 10 g of the mica pigments coated with ceroxalate are heated in a tube furnace in a quartz boat in an N ₂ stream (200 cm ³ / min) to 900 ° C. An H ₂ S stream (200 m ³ / min) is then additionally passed through the system for 4 h at 900 ° C. When the reaction is complete, the product is allowed to cool to room temperature with inertization (N ₂ ). The red-violet pigments produced in this way have a β-Ce ₁₀ S ₁₄ O coating.

Claims (12)

1. Sulfide and oxysulfide pigments based on platelet-shaped substrates, characterised in that the substrate is coated with yttrium sulfides and/or one or more rare-earth metal sulfides of the formula M₂S₃ or the corresponding oxysulfides of the formula M₂S_3-xO_x, in which M is at least one element selected from the group formed by the lanthanides and yttrium, and 2.5 < x < 0.05.
2. Pigments according to Claim 1, characterised in that the rare-earth metal sulfide or oxysulfide is a sulfide or oxysulfide of cerium, neodymium, praseodymium, samarium, gadolinium, terbium, dysprosium, erbium or thulium.
3. Pigments according to Claim 1 or 2, characterised in that the platelet-shaped substrate comprises uncoated or mono- or multicoated mica platelets, SiO₂ flakes, TiO₂ flakes, Al₂O₃ flakes, glass platelets, graphite, bismuth oxide chloride or platelet-shaped metal oxides.
4. Pigments according to one of Claims 1 to 3, characterised in that the mass of rare-earth metal sulfide or oxysulfide, based on the total pigment, is from 1 to 400% by weight.
5. Pigments according to one of Claims 1 to 4, characterised in that the rare-earth metal sulfide layer or oxysulfide layer is doped with one or more alkali and/or alkaline earth metals.
6. Pigments according to Claim 5, characterised in that the doping element is present in amounts of from 0.01 to 1.0% by weight, based on the sulfide layer or oxysulfide layer.
7. Pigments according to Claim 5 or 6, characterised in that the doping element is sodium or potassium.
8. Pigments according to one of Claims 1 to 7, characterised in that a platelet-shaped substrate has a layer of sodium-doped cerium sulfide Ce₂S₃.
9. Process for the preparation of pigments according to Claim 1, characterised in that a solution of a salt of a rare-earth metal and/or of yttrium and, if desired, an oxalic acid solution are added to an aqueous suspension of a platelet-shaped substrate, and, if desired, a dopant in solid form or in the form of an aqueous solution is added to the suspension, where the pH of the suspension is, if necessary, kept substantially constant in a range which effects hydrolysis of the added salt by simultaneous addition of a base, and the pigment coated in this way with an oxide or oxide hydrate or oxalate is separated off, washed, dried and, if desired, firstly calcined at from 400 to 800°C and finally converted into the sulfide or oxysulfide at from 550 to 1200°C in the presence of sulfur-containing compounds, CS₂, sulfur or hydrogen sulfide.
10. Process according to Claim 9, characterised in that the dopant is one or more alkali and/or alkaline earth metal salts.
11. Use of the pigments according to Claim 1 in formulations such as automotive finishes, paints, coatings, printing inks, plastics and in cosmetics.
12. Formulations comprising pigments according to one of Claims 1 to 8.